Stealth vs Starvation?

[TwoBits]

Does stealth somehow mitigate the effects of lack of supplies?

OK, here's my situation, albeit with some small attempt to maintain my in-game anonymity:

I'm being raided by a large force of 'super-stealth' units (around 100 or so, many of which are mounted). They are operating in provinces that are either already 'waste land', or where I have previously pillaged things down to what I thought were 'inhospitable' levels (only a few hundred pop. left, with supply levels around, say, 50 or so).

This force is not led by leaders with nature magic, nor do they have supply granting magic items. Yet they have been in my territory for at least two turns (and possibly longer, depending on the nature of their approach - being stealthed, I have no real idea of how they got into my lands), and after checking the last battle replay, I see that only a portion of their forces are just now being hit with the 'starvation' tag (meaning, as I click about randomly on their units, some seem to be starving, and others not). None seem to be afflicted with disease (which is of course what I'd been hoping for with my campaign of preemptive pillaging).

Is this possible? I'd always thought that either the entire army was starving or not - not just some units. Having done a commander count, I'm positive this force has not been reinforced with new, supplied, units. Besides, I found starving and non-starving units mixed together in the same 'squad', meaning, only some units in the same army have been afflicted by hunger, while others seem to be perfectly fine and well-fed, much less rendered abject by diseases and privation, like I'd expected!

So, is there something I'm missing here, either in terms of game mechanics (am I misunderstanding the supply rules?) or game play (is my foe somehow supplying some of his forces in a way I don't understand, or slipping in fresh, supplied forces to the same army, again in a way I don't understand?)?

Or do stealth forces truly have some sort of bonus when it comes to operating in low supply environments?

Any timely info on this topic would be very, very appreciated!